Bias question

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 6:29 pm

What two points do I measure at to get the bias reading?

rockstah · Post by **rockstah** » Tue Feb 07, 2006 6:32 pm

sweetwilliam wrote:What two points do I measure at to get the bias reading?

the way i do my bias:

meter on 2dcv setting

black to chassis

with 1ohm resistors installed on power tubes( pins 8 and 1 are tied together and resistor goes from pin 1 to ground), red to tube side of the resistor.

hope this helps

Mark

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 6:36 pm

At the moment, I don't have 1 ohm resistors, but I can get a mA reading on my multimeter. Need to get 24 mA for 6V6's.

rockstah · Post by **rockstah** » Tue Feb 07, 2006 6:38 pm

sweetwilliam wrote:At the moment, I don't have 1 ohm resistors, but I can get a mA reading on my multimeter. Need to get 24 mA for 6V6's.

1. if you dont have the resistors how r u readng it?

2. if you are reading it then why the thread on how to read it?

Mark

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 6:48 pm

That's just it. I can't get a reading. When I go to measure current, I get nothing. I'm not sure that I'm using the right points to do it.

rockstah · Post by **rockstah** » Tue Feb 07, 2006 6:50 pm

sweetwilliam wrote:I can get a mA reading on my multimeter.

??

Eoin · Post by **Eoin** » Tue Feb 07, 2006 6:54 pm

You can only measure current in series, so at whatever point you want to make the measurement you have to unsolder the connection and put the multimeter in between.

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 6:54 pm

I know. I'm baffled. If I set it to VDC I get around -10 to -11 volts after the bias splitter. If I try to measure current, nothing.

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 6:55 pm

I think I need to get some 1 ohm resistors and be done with it.

rockstah · Post by **rockstah** » Tue Feb 07, 2006 6:56 pm

time to get some 1ohm resistors on the tubes or get one of these i guess - http://www.amp-head.com/product_info.ph ... ucts_id=30

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 7:03 pm

The resistor would go in place of the ground connection?

rockstah · Post by **rockstah** » Tue Feb 07, 2006 7:05 pm

1ohm metal film resistors

on an el34 amp:
tie pins 8 and 1 together and run the resistor from pin 1 to ground.

not sure about 6v6 tubes.

Mark

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 7:11 pm

Nothing happening on pin 1, at least on JJ 6V6's. I've got an old pair of Emerson brand that have a pin 1, but these JJ's don't. Guess I could just go from pin 8 to ground.

sweetwilliam · Post by **sweetwilliam** » Tue Feb 07, 2006 7:15 pm

Actually, I have a few 1 ohm metal films, but they're only 1/4 watt. Probably not big enough.

novosibir · Post by **novosibir** » Tue Feb 07, 2006 7:17 pm

sweetwilliam wrote:Nothing happening on pin 1, at least on JJ 6V6's. I've got an old pair of Emerson brand that have a pin 1, but these JJ's don't. Guess I could just go from pin 8 to ground.

Right! On 6V6's and 6L6's pin1 (beam forming plates) is internally connected to pin 8

Larry

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